Accessories. 59 



has a ball and socket joint and a sliding bar, by means, 

 of which the lens can be placed in any desired posi- 

 tion. The plane side of the lens should be turned 

 towards the object and the convex 

 towards the source of the illumi- 

 nation, whether it be daylight or 

 artificial by lamp. Latterly Mr. 

 Nelson has suggested improve- 

 ments in the construction of bull's- 

 eye condensers in order to reduce 

 the large amount of spherical 

 aberration which is a necessary 

 accompaniment of the single lens. 

 His improved form consists of 

 either two or three lenses in com- 

 bination, and the advantage ob- 

 tained is well worth the additional 

 outlay. To enhance the effects 

 obtained with opaque objects with 

 these stand-condensers the side 

 silver reflector will be found very 

 convenient. This is attached to 

 either the stage or lamp of the 

 microscope, or fitted between the 

 nosepiece and the objective. It 

 consists of a highly-polished silver 

 parabolic speculum. This reflector 

 is placed by the side of the object, -p IQt 20. Stand Condenser. 

 and light is thrown from the lamp 



through the bull's-eye on to its centre, and then thrown 

 by the reflector on to the object. Most brilliant opaque 

 illumination may be obtained by this means. 



The Lamp. 



This is one of the most important items in microscopy 

 in order to get good effects. The amateur will often be 



